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doc: clarifying unsafe code vs undefined behavior

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Alfie John 2014-11-19 12:43:13 +00:00
parent cf7df1e638
commit e0b0c83138
1 changed files with 8 additions and 9 deletions
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src/doc/reference.md
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@ -1117,13 +1117,13 @@ Rust:
##### Unsafe functions
Unsafe functions are functions that are not safe in all contexts and/or for all
possible inputs. Such a function must be prefixed with the keyword `unsafe`.
possible inputs. Such a function must be prefixed with the keyword `unsafe` and
can only be called from an `unsafe` block or another `unsafe` function.
##### Unsafe blocks
A block of code can also be prefixed with the `unsafe` keyword, to permit
calling `unsafe` functions or dereferencing raw pointers within a safe
function.
A block of code can be prefixed with the `unsafe` keyword, to permit calling
`unsafe` functions or dereferencing raw pointers within a safe function.
When a programmer has sufficient conviction that a sequence of potentially
unsafe operations is actually safe, they can encapsulate that sequence (taken
@ -1143,12 +1143,11 @@ represented with reference-counted pointers in safe code. By using `unsafe`
blocks to represent the reverse links as raw pointers, it can be implemented
with only boxes.
##### Behavior considered unsafe
##### Behavior considered undefined
This is a list of behavior which is forbidden in all Rust code. Type checking
provides the guarantee that these issues are never caused by safe code. An
`unsafe` block or function is responsible for never invoking this behaviour or
exposing an API making it possible for it to occur in safe code.
The following is a list of behavior which is forbidden in all Rust code,
including within `unsafe` blocks and `unsafe` functions. Type checking provides
the guarantee that these issues are never caused by safe code.
* Data races
* Dereferencing a null/dangling raw pointer